


Experimenting

by petitepos



Category: Dr. STONE (Anime)
Genre: Dirty Talk, Exhibitionism, Fluff and Smut, Humiliation, M/M, Power Play, Praise Kink, bottom Gen, just straight up smut, not in that order
Language: English
Status: Completed
Published: 2019-12-18
Updated: 2019-12-18
Packaged: 2021-02-26 07:54:06
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,801
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21846241
Author URL: https://archiveofourown.org/users/petitepos/pseuds/petitepos
Summary: “Gen, can you come inside for a second? I need your help with an experiment.”Or: the one where one of Senku's experiments becomes something more.
Relationships: Asagiri Gen/Ishigami Senkuu
Comments: 15
Kudos: 306





	Experimenting

Senku has been working on figuring out whether or not humans had evolved in any way over the last 3700 years. Currently, he’s comparing bodily functions. Since he and Gen are the only modern men in the kingdom of science he knows the results won’t be reliable, but it’s valuable data nonetheless. He’s already made all of the villagers run laps until they couldn’t continue and measuring their heart rate, and has already conducted the same experiment on himself. The last one left is Gen, who’s currently outside of the lab weaving flower crowns for the children. “Gen, can you come inside for a second?” Gen peeks his head around the corner, flowers in his hair. “Yes Senku-chan?” “I need your help with an experiment.” Gen stands up and walks into the building, a smile on his face. “Oh? Me? A humble mentalist?” Senku smirks, an evil glint in his eye. “Yes you. We’re going for a run.” If Gen could’ve refused, he would.

Twenty minutes later Gen in sprawled on the floor of the lab, panting like a madman. Senku is standing over him, smirking. “Okay mentalist, sit up for a second.” Gen pushes himself up from the floor with great difficulty, keeping his arms planted behind him so he won’t fall back down. Senku crouches down besides him and pushes his coat from his shoulders and looks at him expectantly. Gen just stares at him. “Oi, mentalist, if I’m going to measure your heart rate I need to be able to feel your heart.” The others face remains blank. “Gen, I need you to remove your clothes.” Gen seems to understand what’s going on now, if his reddening face is anything to go by. Knowing that protesting is futile, he starts freeing himself of his layers. Once he’s half naked he leans back on his arms, blush still in place.

Senku takes a second to appreciate the view. When he asked the other villagers to remove their clothes they’d simply pushed the fabric out of the way, or allowed Senku to feel underneath the fabric. The second was never an option with Gen and his tight undershirt, but Senku had never expected him to strip everything until his entire upper body is on show. Looking down at a flushed, panting, and half naked Gen is making it very hard for Senku to concentrate. Still, science comes before bodily needs and irrational crushes, so he squats down and puts his hand on Gens chest. “Senku-chan that’s too cold!” Gen is pouting now, trying to twist his torso away from Senku’s cold touch. “Keep still mentalist, I can’t do my experiment if you’re working against me.” His words don’t help, and Senku gets on top of Gen and uses both of his hands to keep him still. Gen stiffens, wide eyes looking up at him. “S-Senku-chan, what are you doing?” Senku smirks. “If you’re not going to keep still, I’ll just have to help you.”

Gen lies still after that, eyes following Senku as he feels his chest before writing down some numbers on a piece of paper next to them. He gets bored of lying still soon, no matter how much he likes having Senku on top of him, so he starts squirming around again to get the scientist’s attention. The other tells him to knock it off, but there’s no stopping him now. “Senku-chan~, I’m bored, can I-” He gets cut off mid-sentence as Senku pinches his nipple in an effort to get him to shut up. What actually happens is Gen letting out a breathy moan that surprises the both of them. Gen looks mortified, and has brought one of his hands to his mouth. “Senku-chan, that was nothing, I-” Senku cuts him off again by repeating the same action, not letting up when Gen starts whining. “So, the great mentalist has a weakness after all, who would’ve known?” He’s wearing his signature smirk, eyes lighting up as Gen starts moving underneath him. Now this is exhilarating.

Meanwhile, Gen can feel himself getting worked up. He feel so vulnerable like this, half naked with Senku on top of him, pinching and twisting his nipples, not to mention the look on his face. It doesn’t help that he’s been crushing on the scientist since before he joined the kingdom of science and has fantasized about him more times than he can recall. “Ah- Senku-chan, what are you doing?” Senku stops his assault and rests his hands on his chest instead. “Just experimenting mentalist, unless you want me to stop?” There’s an undertone of uncertainty in his voice, not wanting to take this any further if the other doesn’t want him to. It’s silent for a few seconds, but when Gen replies the lust is evident in his voice. “Don’t stop Senku-chan, do whatever you want with me.” Senku slowly pushes him down onto the floor, resting his hands on either side of his head. “Whatever I want to do? You sure?” Gen nods, and before he can register what is happening Senku’s lips are on his. 

The kiss starts uncertain, but it isn’t long before the need that had been building up for so long starts to shine through. Gen’s arms have wound themselves around Senku, pulling him impossibly close, while he has buried one hand in Gen’s hair and another palming him through his pants. The mentalist is moaning into his mouth, getting louder when he bites his lip. So he has a thing for pain huh. Interesting. Senku breaks the kiss and climbs off of Gen, sitting down next to him. “Come here mentalist.” Gen is just about to sit down when Senku stops him. “Strip first.” The other flushes red again, arms wrapping around himself. “Senku-chan, you’re embarrassing me!” Senku just shakes his head and makes a spinning motion with his index finger. “I’m the one who’s in charge of the experiment mentalist, now strip. Or do you want to get punished?” Gen lets out a soft moan and turns around, slowly pulling his pants down before turning around again. He’s suddenly very aware of the fact that he’s completely naked while Senku is still fully dressed. He feels shame creeping up on him, but combined with the way Senku is looking at him it only serves to make him feel hotter. Back in the old days he’s had many partners who were on the dominant side, but he’s never felt the need to submit to someone as much as he’s feeling now. 

Senku smiles at the way Gen is standing in front of him, hands clenched at his side, his head hanging down but eyes looking straight at him. He motions for him to come closer again. Gen sits down on his lap and wraps his legs around Senku, pulling himself as close to the other as he can and softly grinding down on him, his face pressed against his shoulder. Senku chuckles and places his hands on Gen’s hips, guiding his movements. “Eager, aren’t we?” Gen just nods, trying to pull him closer while one of Senku’s hands moves upwards, only his fingertips touching the skin beneath them. “Senku-chan, I need more, I want, hah, please, Senku-chan, more!” Senku buries his hand in white hair and pulls, exposing more of that pale neck in which he sinks his teeth, while pulling Gen even closer against himself. The other moans loudly, hips faltering for a second before frantically searching for a new rhythm. 

“Interesting, you like it when I hurt you mentalist? Like it when I mark you up for the world to see?” Gen honest to god whines when he hears those words spill from Senku’s lips. “Yes! God, Senku-chan, mark me, make me yours, please! Whatever you want!” Senku groans. He never knew Gen would be so eager to submit to him. He’s never really been one for powerplay, although he has experimented with one of his exes when he asked him to. It surprises him how easily he slips into the dominant role and how much he’s getting off on Gen basically asking him to force him into submission ever further. But who is he to deny Gen anything when he is begging him so prettily? With that thought he sinks his teeth into Gen’s neck again, not hard enough to draw blood but enough to make sure the imprints of his teeth are clear against his skin. He starts sucking bruises on every bit of skin he can reach, drinking in the sounds Gen is making. “Fuck! Senku-chan don’t stop, please, more, I need- Ah!! Please!!” 

Senku is painfully hard now, Gen’s lewd words and the way his ass is grinding against his dick not helping. “Mentalist, get off of me for a second.” Gen just holds onto him tighter, a desperate whine leaving his lips. “Don’t make me repeat myself.” The other just moans something along the lines of “so close, feels so good, don’t wanna stop”, showing no intention of listening to Senku. “Don’t tell me I didn’t warn you.” Senku removes his hand from where he still had a bruising grip on Gen’s hip, pulls it back a bit and brings it down on Gen’s ass, hard. His head shoots up and he moans loudly into Senku’s ear, hands gripping his dress tightly. He should’ve know that would happen. “Mentalist, if you don’t listen to me right now I’ll have you watch me get off by myself before sending you away.” Gen does listen to that, quickly untangling himself for Senku and kneeling on the floor in front of him, hands folded in his lap. Senku crouches down in front of him, pressing a hand to his cheek and enjoying the way Gen almost melts into his touch. “Good boy.” He doesn’t miss the shiver that travels through Gen’s body. 

He rumbles through the cabinets for a while before finding what he’s looking for. When he returns Gen is still in the same position, watching his every move. Senku stands in front of him, arms folded. “How do you want to do this mentalist? You wanna bend over for me, sit in my lap, lie down so I can see your pretty face?” Gen sits up on his knees and tugs at his skirt, signalling for him to sit down again so he can sit in his lap. “Wanna be close to you, s nice and warm.” Senku smiles and pulls him in for a soft kiss. “You’re so precious, my sweet mentalist.” Gen kisses him back with barely suppressed need, trying to get as much of their bodies to touch. Senku open the jar that he just retrieved and dips his fingers in it before bringing it down to Gen’s ass. “Hah, Senku-chan, what’s that?” A finger makes its way inside, forcing a moan out of him. “Coconut oil, the best lube you can get in the stone age.” A second finger soon joins the first one, and Gen starts to try and fuck himself on them. He rolls his hips in an effort to get more friction on his dick, and to get Senku to push his fingers in deeper, slowly losing his mind to the sweet sensations. 

“You should see yourself right now mentalist, such a slut for my fingers, not even fucking you yet.” Gen picks up the pace, wishing he had a mirror so he could watch himself come undone with nothing but Senku’s talented fingers. He can feel his mind getting fuzzy while Senku continues to whisper words of praise into his ear and curling his fingers just right. It almost feels like he’s floating, only able to focus on pleasing Senku, and he lets himself get lost in the feeling. “Just for you Senku-chan, your slut, anything for you!” The scientist curses and starts scissoring his fingers faster, getting impatient. Gen is almost bouncing in his lap, face pressed into Senku’s neck and his tongue lapping at the skin. “Senku-chan, I’m ready please just, fuck me, hahhh, please!” Senku pulls his fingers out, threading the fingers of his other hand through Gen’s white hair and pulling him up so they’re face to face. 

“Fuck, mentalist, you look so good like this, can’t wait to be inside you, gonna make you feel so good.” Gen’s eyes are glazed over, looking lost in his own little world. Senku kisses him hard while pushing his own skirt up and using the oil on his hand to lube himself up, before guiding himself to Gen’s entrance. “You ready mentalist?” Gen responds by pushing back against him and trying to kiss him again. Senku chuckles. “So impatient, you sure you deserve this? Maybe I should make you work harder.” Tears are now falling from Gen’s eyes, desperate for Senku to give him what he wants, why won’t he give him what he wants? “No, please Senku-chan, ‘ve been so good for you, I need- ha, please!” 

Senku finally enters him, not bothering to go slow, knowing that the pain will only turn Gen on more. He hold him close to his own body, fucking up into him hard. He hopes that nobody is near the lab right now with the way Gen is practically screaming. His hands are everywhere, desperately looking for something to hold onto, to ground him. Senku doesn’t give him the chance to catch his breath, sucking more bruises over the ones that are already there before grunting into his ear. “You feel so good around me mentalist, so perfect for me, so pretty, if only the others could see you right now.” Gen tightens around him and Senku smirks. Bingo. “You’d like that wouldn’t you, you dirty mentalist? Everyone seeing you bounce on my dick like a perfect little whore? Bet that’s why you’re being so loud huh, hoping they will hear.” The other tries to protest between moans, but his body is betraying him. “S-Senku, hahhh, chan, I- not true, fuck!” Senku moves his arms so he can grab Gen by the waist, Gen wrapping his arms around his neck so he won’t fall backwards. Now Senku is pulling him down everytime he moves his hips up, locking eyes with Gen. “Don’t lie mentalist, should I call Chrome? I bet he’d love to let you suck him off while I’m fucking you, telling you how pretty you are, how good you’re doing. Bet you let yourself be fucked like this all the time by Tsukasa and his men, such a perfect little slut, just begging for it all the time, taking it so well for them.” 

Gen tenses, and Senku worries that he has taken it too far with that last bit, but Gen is tightening even further and cumming between them, letting out soft whimpers and pressing his forehead against Senku’s. The scientist curses and with a few quick thrusts he’s cumming as well, finishing deep inside Gen. They sit like that for a while, embracing each other and coming down from their high. It’s Senku who moves first, softly laying Gen down and pulling out of him, ignoring his weak cries and fetching a towel from a nearby bowl of water. “It’s okay, I’m not going anywhere, just cleaning you up.” Gen mumbles something he can’t quite understand and reaches for him. Senku smiles softly, he’d really done a number on him huh? He makes sure to wipe the sweat from his brow first, then cleaning up his chest and cleaning him out, ignoring the way Gen tries to squirm away from his fingers. When he’s satisfied he tries to wipe the cum from his own clothes, cleaning it as best as he can. 

Gen is still whining and reaching for him. Senku gets his overcoat and wraps the mentalist in it before lifting him bridal style with great effort, Gen snuggling into his chest. The walk to his hut has never seemed longer, the stares they were getting not helping. When they pass Chrome Senku can’t help but flush, embarrassed by the things he’s just said about him in the heat of the moment, especially with the way he and Gen must look right now. They finally reach his hut and Senku softly lays Gen down on his bed. He gets rid of his own clothes and pulls the blankets over the both of them. Gen has almost drifted off to sleep, looking up at Senku through lidded eyes. “You’re amazing Senku-chan.” The scientist smiles softly and pressed a kiss to Gen’s lips. “You’re not bad yourself mentalist, you did so well for me.” Gen smiles sleepily before pressing his face against Senku’s chest, feeling arms wrap around him and pulling him even closer. “Love you Senku.” Senku smiles and pets his head. 

“I love you too Gen”

**Author's Note:**

> So. I wanted more Sengen, there hasn't been a smutty one in a while, so I decided to write one myself. This is just, pure thirst, almost 3000 words of pure self indulgence. What is their motivation? Their backstory? Who knows, not me! 
> 
> Thanks for reading, hope you enjoyed this piece of absolute filth <3


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